Deposition of cobalt and nickel sulfide thin films from thio- and alkylthio-urea complexes as precursors via the aerosol assisted chemical vapour deposition technique

Abstract

We report the synthesis of Co(II) and Ni(II) thiourea and alkylthiourea complexes by reacting the metal salts (CoCl2 and NiCl2) with the thiourea, phenylthiourea and dicyclohexylthiourea ligands in a 1:2 ratio. The complexes, [CoCl2(CS(NH2)2)2] (I), [CoCl2(CSNHC6H5NH2)2 (II) and [CoCI2(SC(NHC6H11)2)2] (III), [NiCl2(CS(NH2)2)2] (IV), [NiCl2(CSNHC6H5NH2)2] (V) and [NiCl2(SC(NHC6H11)2)2] (VI) were characterized by C, H, N analysis and Fourier transform infrared spectroscopy. Thermogravimetric analysis shows that all complexes undergo a two step decomposition process except for [NiCl2(CSNHC6H5NH2)2] (V) which decomposes in a single step. The complexes were used as single-source precursors for the deposition of cobalt sulfide and nickel sulfide thin films by aerosol assisted chemical vapor deposition at temperatures between 350 an 500°C. The crystallinity of the films was determined by X-ray diffraction and their morphology was determined by scanning electron microscopy. The morphology of the cobalt sulfide thin films varies from randomly oriented platelets, to granulated spheres and cubes as the precursor and deposition conditions are changed. For nickel sulfide, the [NiCl2(CS(NH2)2)2] (IV) complex gave rods whereas the [NiCl2(CSNHC6H5NH2)2] (V) produced spherical particles.